Method for Producing a Yarn in a Jet Spinner

ABSTRACT

During a jet spinning method, the rotating fibre ends or the subsequent wound fibres of the spun yarn ( 70 ) cause a spinning tension F s . In tests, a direct correlation has been established between the spinning result and the spinning tension F s . The aim of the invention therefore is to provide a method for spinning yarn in a jet spinner that permits an ideal spinning tension F s  despite high spinning speeds, thus achieving an optimal spinning result, in particular with regard to the yarn quality. According to the invention, a jet spinner is operated with a spinning tension F s &lt;20 cN by means of a configuration of spinning box elements.

The invention relates to a method for producing a yarn in a jet spinneraccording to the preamble of patent claim 1.

The present invention relates to the field of jet spinners. Jet spinnershave a multiplicity of spinning stations. In each spinning station, ayarn is spun from a longitudinal fiber structure which is supplied. Inthis case, the longitudinal fiber structure is first refined, that is tosay the fiber quantity per unit length is reduced by drafting. Then, inthe spinning station, the refined fiber composite is spun into a yarn byimparting twist to it. For this purpose, the spinning station has afiber guide element which guides the fiber composition into a swirlchamber where a yarn is produced on a spindle by means of the knownvortex jet spinning method.

Tests have shown that there is a direct relation between the spinningtension and the spinning result. FIG. 1 shows a diagrammaticillustration of the components of a jet spinner. As explained above, thelongitudinal fiber structure 1 is refined in a drafting arrangement 69,spun into a yarn 70 in the spinning box 5 and supplied to a yarn bobbin68 via a thread transfer device 67 by means of take-off rollers 64. Theterm spinning tension F_(s) is understood in this context to mean theforce F_(s), to be given in the units [N] or [cN], which acts on theyarn between the spinning box 5 and take-off 63.

For a further explanation, then, reference is made to FIG. 2. Thespinning box 5 has a swirl chamber 10 in which the air flowing inthrough the air inlet port 61 generates a swirl flow which rotatesaround edge fibers 62 located on the surface of the fiber composite 1and thereby spins the fiber composition 1 into a yarn 70. Theabovementioned spinning tension F_(s) is caused mainly by the run-on ofedge fibers 62 at the inlet mouth 9 of the spindle 7. These forcesconsequently have a particular characteristic which is basicallydifferent from the tension characteristics of other methods, such as,for example, ring, rotor or two-nozzle spinning.

Since, in the jet spinning method (an example of a machine correspondingto this may be gathered from the publication EP 1 335 050 A2 [2]),essentially the rotating fiber ends or the subsequent wrap-around fibersof the spun yarn 70 cause the spinning tension F_(s), there is a directcorrelation between the spinning result, that is to say the yarnproduced, and the actual measurable spinning tension F_(s). The term“spinning result” embraces the properties of yarn quality and spinningprocess reliability. By reduction in the spinning speed, the spinningtension can also be reduced to values which permit an improved spinningresult. However, in the case of the high spinning performances required,with spinning speeds v_(L)>300 m/min required for this purpose, this, onthe one hand, is not practicable and, on the other hand, leads to animpairment of the spinning result for the following reason: the edgefibers should ideally be spun into a yarn 70 at an angle ofapproximately 45° around the fiber composite 1. This angle, then, takinginto account the air vortex, is determined essentially by the spinningspeed, and this must therefore move within a customary range toward 300m/min.

The object on which the present invention is based is, therefore, tospecify a method for spinning a yarn in a jet spinner, in which, despitehigh spinning speeds, an ideal spinning tension can be set, with theresult that an optimal spinning result, particularly with regard to theyarn quality, is achieved.

This object is achieved by means of the method specified in patent claim1.

By virtue of the method parameters according to the invention, accordingto which the spinning tension F_(s) has a value range F_(s)<20 cN, amethod is provided which in the case of high speeds allows a spinningtension which ensures, in particular, high reliability, so that, forexample, the risk of yarn breaks is greatly reduced.

In order to achieve this sought-after value range for the spinningtension F_(s) and consequently to optimize the spinning result, forexample, one or more of the following measures may be taken:

-   -   Adaptation of the spinning draft s_(v) between the drafting        arrangement exit and the take-off rollers downstream of the        spinning box, so that s_(v)≦1.0.    -   Adaptation of the compressed air pressure p of the air which        flows into the swirl chamber to values of 3 to 6 bar, preferably        of 4 to 5 bar.    -   Achievement of a high suction action by the air vortex generated        in the swirl chamber, in order to suck in air from the gusset        region downstream of the exit nip line of the drafting        arrangement. There are various configuration possibilities for        this purpose which are described in the embodiments listed        below.    -   Optimal configuration of the swirl chamber. There are various        configuration possibilities for this purpose, too, which are        likewise specified in the exemplary embodiments listed below.

Moreover, advantageous refinements of the invention are specified infurther dependent claims.

The invention is explained in more detail below by way of example, withreference to drawings in which:

FIG. 1 shows a diagrammatic illustration of the components of a jetspinner;

FIG. 2 shows a partial illustration of a spinning box, particularly toexplain the entry of a fiber composite into the spindle;

FIG. 3 shows a fiber conveyance duct with a tunnel lining;

FIG. 4 shows a more detailed illustration of the shoulder of the tunnellining and, of the air inlet port in the first embodiment;

FIG. 5 shows a more detailed illustration of the shoulder of the tunnellining and of the air inlet port in a second embodiment;

FIG. 6 shows an illustration of a fiber guide face having a deflectionedge, in a fiber guide duct.

FIG. 1 shows a diagrammatic illustration of the components of a jetspinner: the speeds which occur are shown by v_(exit) and v_(take-off),and reference symbol 71 indicates the location at which the methodparameter, spinning tension F_(s), relevant to this invention occurs.

FIG. 2 shows a detailed illustration of a spinning box 5, such ascorresponds to the prior art and has already been explained in thedescription introduction.

FIG. 3 shows a first configuration within a spinning box 5 to ensurethat the desired spinning tension F_(s) is achieved. The spinning box 5has a fiber guide element 3 and, thereafter, a spindle 7 with a yarnguide duct 8. The fiber guide element 3 is surrounded by ahollow-cylindrical tunnel lining 17. The tunnel lining 17 may beproduced in one piece or in a plurality of pieces. The fiber conveyanceduct 4 is encased by the tunnel lining 17. The tunnel lining 17 isshaped in such a way that a shoulder 18 toward the swirl chamber housing15 occurs at the end of the fiber conveyance duct 4. The end face of theshoulder 18 serves as a guide face for the fluid, normally air, emergingfrom the jet nozzles 13.1. The outlet ports for the jet nozzles for thefluid into the swirl chamber 14.1 have an elliptic shape. In this case,the fiber guide element 3 and the associated tunnel lining 17 areinstalled in the swirl chamber housing 15. As is also shown in thefollowing FIGS. 4 and 5, the swirl chamber housing 15 does notnecessarily also have to comprise the fiber guide element 3 and itstunnel lining 17. The two last-mentioned elements may also have aspecific housing which is contiguous to the swirl chamber housing 15(see FIG. 5). Overall, four individual jet nozzles 13.1 are provided.The jet nozzles 13.1 have an angle of inclination a with respect to thefiber transport-direction 19. The angle of inclination a lies in a valuerange of 45° to 88°. In this first embodiment, the angle of inclinationof the end face of the shoulder 18 with respect to the material flowdirection has the same amount. In this case, it can be seen clearly howthat end face 20 of the fiber guide element 3 which is contiguous to theswirl chamber 14.1 has the same angle of inclination with respect to thematerial flow direction 19 as the bores of the jet nozzles 13.1.

FIGS. 4 and 5 show two further embodiments of the shoulder of the tunnellining to ensure that the desired spinning tension F_(s) is achieved.The swirl chamber housing 15 in this case adjoins a housing 32 for thefiber guide element 3 and the tunnel lining. The embodiment shownaccording to FIG. 4 possesses a tunnel lining 26 which is shaped in sucha way that the shoulder 29 occurs at the end of the fiber conveyanceduct 4 with an angle of inclination β. The tunnel lining 26 preferablyhas a thickness (a) which lies in a value range of 0.1 to 3 mm. The boreof the jet nozzle 13.1 is arranged in the immediate vicinity of the endface of the shoulder 29 in the swirl chamber housing 15. The shoulder 29is in this case arranged so near to the opening to the jet nozzle 13.1that the end face of said shoulder serves as a guide face for theemerging flow. The shoulder 29 is arranged in alignment with the borewhich is itself arranged in alignment with the inner face or surfacearea of the swirl chamber 14.1, so that the bore 13.1 runs “tangentiallyin alignment” into the inside of the swirl chamber housing 15 ortangentially into the swirl chamber 14.1. However, angles of inclinationα with respect to the material flow direction which lie in a value rangeof 60° to 70° are preferred. The angle of inclination β of the end faceof the shoulder 29 may have a different value from the angle ofinclination α. The most suitable angle of inclination β can best bedetermined empirically for the actual application. Tests have shownthat, in most cases, an angle of inclination β which has the same valueas the angle of inclination α is suitable. However, a design with ≠#β isalso possible. In FIG. 5, the bore 13.1 is arranged at a distance d fromthe shoulder 31 of the tunnel lining 28. The distance d in this caselies in a value range of 0.5 mm to 2 mm, preferably 0.9 mm to 1.3 mm,preferably 1.1 mm.

FIG. 6 shows a cross section through a spinning box 5 in anotherembodiment, in order to achieve the method parameter value according tothe invention of the spinning tension F_(s)<20 cN. The fiber guideelement 3 c shown has a fiber guide face 16 with a deflection point 72.The deflection point 72 is formed by the fiber guide face 16: the fiberguide face 16 in this case consists of two planar faces, the commonintersection line of which forms the deflection point 72. By virtue ofthis configuration of the fiber guide face 16, the fibers of the fibercomposite 1 (not illustrated in FIG. 6) are guided in an arrangement inwhich they lie essentially flat next to one another. The fiber dischargeedge 6 also makes a contribution to this flat arrangement. Thedeflection point 72 is in this case dimensioned such that the fibers ofthe fiber composite 1 are deflected in such a way that the free fiberends of the fibers which are located in the fiber composite can liftoff. At the deflection point 72, both the front and the rear fiber endsabove all of those fibers which are located on the surface of the fibercomposite 1 or directly below it are lifted off. At the deflection point72, both front and rear fiber ends are lifted off. By fiber ends beinglifted off at the deflection point 72, the number of free fiber ends inthe fiber composite rises. The term “free fiber ends” is to beunderstood as meaning those ends which do not lie within the staplefiber composite or are not connected to other fibers and canconsequently be picked up by the swirl flow. Due to the rise in thenumber of free fiber ends, the number of wrap-around fibers in the yarnand the quality of the spinning process per se are increased. Thisconfiguration of the fiber guide face surprisingly has a furtheradvantage, as compared with the prior art. The result of the reductionin the cross section A of the fiber conveyance duct 4 within a regionwas that the air quantity V flowing through was surprisingly increased.Owing to the increased air quantity V, fiber guidance between the exitrollers and the entrance of the fiber guide element 3 c, that is to sayupstream of the fiber guide element 3 c, can be appreciably improved.The number of production interruptions caused by breaks in the fibercomposite directly downstream of the exit rollers, can thereby bereduced. It was likewise possible to detect a measurable improvement inthe yarn quality. Tests have shown that particularly good results areachieved when the cross section A of the fiber conveyance duct 4 remainsconstant as far as the deflection point 72 and, beyond the deflectionpoint or additional edge 72, the following cross section B of the fiberconveyance duct 15 increases. The area of the cross section A of thefiber conveyance duct 4 as far as the deflection point 72 preferablylies in a value range of 0.5 mm² to 10 mm². Table 1 contains dimensionalparticulars relating to the variables C, D, E and F contained in FIG. 6,which make it possible to have a spinning tension F_(s)<20 cN. TABLE 1Dimensional particulars relating to the embodiment according to FIG. 6Preferred Symbol Value value Description unit range range Horizontaldistance between C 1 . . . 4 1.5 . . . 2.5 deflection point 72 and fiber[mm] discharge edge 6 Vertical distance between D 0.2 . . . 1   0.4 . .. 0.7 deflection point 72 and fiber [mm] discharge edge 6 Horizontaldistance between E 0.1 . . . 1   0.3 . . . 0.7 fiber discharge edge 6and inlet [mm] mouth 9 Vertical distance F between F 10 . . . 40 fiberdischarge edge 6 and [in % center line of yarn guide duct 8 diameter ofyarn guide duct]

In order to make it possible to have the desired spinning tensionF_(s)<20 cN, the air (fluid) to be supplied preferably has a pressure pwhich lies in the following value range:3 bar<p<6 bar.

In a further refinement of the present invention, a spinning draftS_(v)≦1.0. In this case, the spinning draft S_(v) is defined by thefollowing quotient:S _(v):=v_(take-off) /v _(exit).

In this case:

-   -   v_(take-off) means the rotational speed of the take-off rollers;    -   v_(exit) means the rotational speed of the exit rollers.

The condition S_(v)≦1.0 means that the circumferential speed of thetake-off rollers 64 must be at most equal to that of the exit rollers 2of the drafting arrangement 69. It is therefore possible to obtain thiscondition because, during the spinning of the fibers, the fibercomposite slightly loses length. S_(v) in this case preferably lies inthe range of 0.96 to 1.0.

A further preferred embodiment of the invention arose from numerousspinning tests. Moreover, in these spinning tests under variousoperating conditions (such as different spinning speeds and yarnfinenesses), optimizations of the elements of the spinning device andanalyses of the spun yarn quality, it was possible surprisingly to finda relation which, on the basis of the operating conditions of spinningspeed and yarn fineness, predetermines an optimal spinning tensionF_(s,optimal): $\begin{matrix}{{F_{s,{optimal}} = {{6.6\quad{cN}}\quad + {0.05{\frac{{cN}\quad g}{m} \cdot \left( {{100\frac{m}{g}} - {Nm}} \right)}} +}}\quad} \\{0.0096{\frac{{cN}\quad\min}{m} \cdot \left( {v_{L} - {350\frac{m}{\min}}} \right)}}\end{matrix}\quad$in which:

-   -   F_(s,optimal)=optimal spinning tension in [cN]    -   Nm=yarn fineness in metric number [m/g]    -   v_(L)=yarn delivery speed in [m/min]

This relation is not a physical formula which necessarily arises due tothe operation of the spinning station. Instead, this formula indicatesthe optimal spinning tension which is to be achieved on account of theoperating conditions of yarn delivery speed at the exit of the spinningmachine and desired yarn fineness (what is known as the “metric number”of the spun yarn in [m/g]) by the adaption of the most diverse possibleelements of the spinning machine. In other words, if a spinning machineis operated at a specific yarn delivery speed and a specific yarnfineness is established (for example, by setting the draftingarrangement), this does not mean that this automatically results in aspinning tension according to the abovementioned relation. A completelydifferent actual spinning tension F_(s) will therefore be obtained. Ayarn quality will also likewise not be optimal. What therefore has to bedone is to vary the actual measurable spinning tension F_(s) by means ofvarious measures described on the previous pages, such that its valuecorresponds to the amount of the optimal spinning tension F_(s,optimal)calculated by means of the above formula. This results in a yarn ofoptimal quality.

The following table 2 contains in the middle column the optimal spinningtension F_(s, optimal) calculated from the metric number and spinningspeed; the spread values defined as ±20% are given in the first twocolumns. TABLE 2 Table of values with the calculated optimal spinningtension F_(s,optimal) Spinning Spinning tension tension F_(s,optimal)F_(s,optimal) lower limit upper limit Spinning Metric Spinning (−20%) in(+20% in tension number mN speed v_(L) [cN] [cN] F_(s,optimal) [cN][g/m] [m/min] 7.664 11.496 9.580 50 400 7.110 10.666 8.888 60 380 6.4809.720 8.100 70 350 5.696 8.544 7.120 80 300

The teaching according to the invention can be implemented by means of afree combination and adaption of the configuration, explained above inFIGS. 3 to 6, of the spinning box 5 and of its spinning box elements,such as, for example, the fiber inlet edge 31, fiber discharge edge 29or deflection point 72, and also freely by means of the abovementionedoperating parameters of pressure and spinning draft. By the elementsmentioned in the preceding description and claimed below being adapted,it is possible to bring the actual measurable spinning tension F_(s) toa value F_(s)<20 cN. In a preferred embodiment of the invention, theactual measurable spinning tension F_(s) even has a value whichcorresponds to the amount according to the abovementioned formula forF_(s,optimal).

LIST OF REFERENCE SYMBOLS USED IN FIGS. 1 TO 6

-   1 Fiber, fiber composite, staple fiber composite-   2 Pair of exit rollers, exit rollers-   3, 3 c Fiber guide element-   4 Fiber guide duct, fiber conveyance duct-   5 Spinning box-   7 Spindle-   8 Yarn guide duct-   9 Inlet mount of the spindle 7-   10 Swirl chamber-   11 Inflowing air-   12 Drafting arrangement-   13 Fluid device-   13.1 Jet nozzles-   14 Space-   14.1 Swirl chamber-   15 Swirl chamber housing-   16 Fiber guide face, planar fiber guide face-   17 Tunnel lining-   17.1 Half-shell of the tunnel lining-   18 Shoulder-   19 Material flow direction, transport direction-   20 End face of the fiber guide element 3 in the swirl chamber-   23 Center line of the yarn guide duct-   26 Tunnel lining-   28 Tunnel lining-   29 Shoulder with angle of inclination β-   31 Shoulder-   32 Housing for fiber guide element and tunnel lining-   60 Spinning station-   61 Inlet port air flow-   62 Edge fibers-   63 Take-off-   64 Take-off rollers-   65 Friction roller-   66 Thread stop motion-   67 Thread transfer device-   68 Yarn bobbin-   69 Drafting arrangement-   70 Yarn-   71 Location where the spinning tension occurs and is measurable-   72 Deflection point

LIST OF REFERENCE SYMBOLS USED IN FIG. 7

-   20 Nozzle block-   21 Jet nozzles-   22 Swirl chamber-   23 Ventilation duct-   25 Conveying direction of the suction-intake air-   26 Fiber conveyance duct-   27 Fiber conveyance element-   28 Fiber guide face-   29 Fiber discharge edge-   30 End face-   32 Fiber reception edge-   32 Spindle-   36 Cone of fiber conveyance element 27-   37 Carrying element for a fiber conveyance element 27-   38 Center line of jet nozzles 21 and blowing direction-   39 Fiber conveyance roller-   45 Yarn guide duct-   47 Center line

LIST OF SYMBOLS USED

-   v_(take-off) Rotational speed of the take-off rollers-   v_(exit) Rotational speed of the exit rollers-   α Angle of inclination of the jet nozzles with respect to the fiber    or material transport direction-   β Angle of inclination of the shoulder with respect to the material    flow direction 19-   a Thickness of the tunnel lining 26-   d Distance between jet nozzles 13.1 and shoulder 31-   A Cross section upstream of deflection point-   B Cross section downstream of deflection point-   C Distance parallel to the center line 23 from the deflection point    72 as far as the fiber discharge edge 6-   D Distance vertically with respect to the center line 23 from the    deflection point 72 as far as the discharge edge 6-   E Distance parallel to the center line 23 from the fiber discharge    edge 72 as far as the inlet mouth 9 of the spindle 7-   F_(s) Spinning tension in [cN]-   F_(s,optimal) Optimal spinning tension in [cN] according to formula-   F Distance vertically with respect to the center line 23 from the    fiber discharge edge 72 as far as the center line 23 of the yarn    guide duct 8-   G Width of the reduced fiber discharge edge 6-   Nm Metric number in [m/g], length per mass; reference in [1]-   p Pressure in [Bar]-   S_(v) Spinning draft-   v_(L) Spinning speeds in m/min

LIST OF ABBREVIATIONS USED

ISO International Standard Organization

LIST OF UNITS USED

Bar Pressure; ISO dimension unit N, cN Newton, Centi-Newton; ISOdimension unit m Meter; ISO dimension unit min Minute

LITERATURE SOURCES

-   [1] Fachwissen Bekleidung, 5th edition ISBN 3-8085-6205-6; 1998    Verlag Europa-Lehrmittel, Nourney, Vollmer GmbH & Co., 42781    Haan-Gruiten-   [2] EP 1 335 050 A2 Textile processing machine with a fiber    conveyance duct and with a fiber guide face; Maschinenfabrik Rieter    AG, 8406 Winterthur.

1. A method for producing a yarn (70) from a fiber composite (1) in ajet spinner which contains: a pair of exit rollers (2); a spinning box(5), following the pair of exit rollers (2) in the spinning direction,for spinning a yarn (70), the spinning box (5) containing: a swirlchamber (14.1) having a spindle (7) and containing at least one airinlet port (13.1, 61); a following take-off (63), containing take-offrollers (64), for leading away the yarn (70), a spinning tension F_(s)being exerted on the yarn (70) by the latter being led away;Characterized by the method parameter: the spinning tension F_(s) hasthe following value range: F_(s)<20 cN. 2-13. (canceled)